1. Field of the Invention
The present invention is directed to a method and arrangement for determining the number of normal imprints implementable with a remaining ink quantity that can be generated by a device having at least one ink jet print head. The invention can be employed for determining the ink supply in ink tank cassettes for postage meter machines that print with an ink jet print head and allows the maximum utilization until the ink tank cassette is replaced.
2. Description of the Prior Art
Postage meter machines have been known since the 1920""s and are still being constantly perfected. The printing principle has changed from original, purely mechanical solutions with printing drums to electronic solutions with thermal transfer or ink jet printing head. The franking imprint must be capable of being read visually and by machine by the postal authorities in order to be able to verify the payment of postage.
An ink that has not been inspected by the manufacturer or not approved by the manufacturer represents a risk to the legibility of the franking imprint. At time intervals, the used ink must be replaced by new ink, or the ink cassette must be replaced. It is in the interest of the manufacturer""s customers and of the postal service to use qualitatively high-grade, proper material.
Indicating an impending change of consumable via a display is disclosed; in German Published Application 195 49 376, wherein sensors are used for determining the remaining amount of an inking ribbon on inking ribbon cassette for a thermal transfer printer or to count the number of imprints with the controller of the thermal transfer printer. This solution, however, is only suited for a thermal transfer postage meter machine, such as for the model Type T1000 offered by Francotyp-Postalia AG and Co., and cannot simply be transferred to postage meter machines with ink jet printers, due to the non-linear relationship between the remaining quantity of ink and number of imprints in such machines.
German Patent 196 13 944 discloses an ink cassette with two approximately identically constructed ink reservoirs that is suitable for the JetMail(copyright) type of postage meter machine also offered by Francotyp-Postalia AG and Co. One ink reservoir serves for disposal of ink collected during priming. The other ink reservoir serves for ink supply and has an end of ink detection with two electrodes, but does not supply information about the filling level either before or after the end signal. A perforation encoding that has also been disclosed does not offer adequate protection against a utilization of an ink tank cassette that is not authorized by the manufacturer of the postage meter machine.
And end of ink detection with electrodes is known from German Patent 27 28 283. Two electrodes for a comparative measurement and a separate electrode for a conductivity measurement for signaling the end of ink are introduced into the floor of the ink reservoir. The transfer impedance between these electrodes is measured with an electronic circuit and is interpreted. The electrodes are arranged in troughs that are formed in the reservoir base. A pre-condition for the use of such an end of ink recognition is the employment of an electrically conductive ink. Such sensors for detecting the end of ink already supply the JetMail(copyright) postage meter machine with an end signal when a maximum of 200 frankings are still possible in order to avoid an incompletely printed franking imprint that has already been debited due to lack of ink. However, a cleaning with ejection (priming) and/or extraction of ink is then no longer possible. The end signal is usually emitted too late to re-order an ink tank when large quantities of mail are processed, and too early when small quantities of mail are processed.
Cassette-shaped containers with ink fluid, inking ribbon or toner are disclosed in U.S. Pat. No. 5,365,312, having an integrated circuit chip with an electronic memory for a code identifying the reservoir, for expiration data and other data, as well as with a counter in order to identify the consumption during printing by counting the individual print pulses, which correspond to the drops of ink that are printed out (ejected). The integrated circuit stores the current filling status and this can be read out and displayed by the printer controller. A reprogramming of the chip and a refilling of the container, however, are not possible. The ink cassette with the chip counts the individual drops and allows use in office printers. The high technical outlay for counting drops, however, is justified only for printing wherein one must expect extremely large differences in consumption for different print images. Due to the large differences in the nature of the print images, however, no conclusion can be made regarding the number of printings that are still possible with a remaining quantity of ink.
European Application 875 862 discloses an ink jet print head for postage meter machines that carries an integrated ink tank and a connector with many contacts and a chip for storing a head identification number and a count. The count corresponds to the number of maximally possible franking imprints, and franking can be carried out with the postage meter machine only when the head identification number is authorized and the maximum number of franking imprints has not yet been reached. This solution can be utilized for ink jet printer postage meter machines only because an essentially constant ink consumption can be expected for franking, particularly stacks of mail. Only the ink consumption is indicated. The user of a postage meter machine, however, would like to be certain that a franking imprint that has been debited can always be completely printed, i.e. even when the end of ink is near. The above solution therefore is unsuitable for ink jet printer postage meter machines. Counting the (normal) imprints cannot supply any information about the number of possible imprints with the amount of ink remaining in the ink tank because, given a low through medium number of frankings per day, the consumption of ink due to the cleaning procedure predominates, which reduces the number of possible imprints per ink tank fill. Given piezo ink jet print heads, a large part of the ink is lost in cleaning with priming and extraction and cannot be re-supplied to the head.
U.S. Pat. No. 5,856,834 discloses a device and method for monitoring the ink consumption in an ink cartridge of a postage meter machine. This device has respective microprocessors in the meter (vault), in the base and at the print head. For cleaning the ink jet print head, the base microprocessor activates a pump station and activates the print head microprocessor and an ASIC for head rinsing. The cleaning and rinsing can be undertaken with different intensities. Compared to a cleaning, a rinsing causes in ink consumption that is reduced by two through four orders or magnitude, which is taken into consideration by software in the base microprocessor. A strong rinsing, xe2x80x9cpower flushxe2x80x9d causes an ink consumption comparable to a franking imprint with an advertizing slogan. Upon initialization of the print head, however, ten times the ink is consumed compared to an intense cleaning, xe2x80x9cpower purgexe2x80x9d. Logically, high ink consumption would be disadvantageous when there is only a small residue of ink in the cartridge. The consumption due to cleaning and rinsing is therefore reduced when the ink consumption falls below a predetermined threshold. Since a safety margin is also embodied in the calculations, the device is able to xe2x80x9cknowxe2x80x9d that the remaining quantity of ink is still sure to suffice for a large number of imprints. The agreement between the calculated and the actual consumption deviates more greatly at the pre-calculated end of ink than at the beginning of the calculation because all influencing factors are not able to be taken into account. If information about remaining ink quantity were determined from the consumption, then the imprecision would be greatest close to the end of ink. The number of imprints for which the remaining ink quantity suffices cannot be predicted. A safety margin must be selected large enough so that the ink is not exhausted earlier than calculated. The refilling of the cartridge with ink is in fact fundamentally possible, but the calculation is fatally compromised if the refilling is implemented imprecisely or incompletely. In this respect, it is disadvantageous when the consumption is only calculated in order to be able to draw conclusions about the remaining quantity of ink therefrom.
The employment of expired, old inks and poor quality inks that are supplied by other manufacturers for refilling, particularly these referred to as pirated products, has not yet be able to be prevented, except when one-time employment of the ink tank cassette is compelled, as proposed in German Patent 196 13 945. An ink connecting line from the ink print head is docked to the container with a hollow needle via a rubber-elastic closure. A cover mechanism that serves as a re-employment block is irreversibly triggered by the hollow needle when the container is pulled off. A refilled ink reservoir can no longer be docked. Unfortunately, this solution also prevents the re-employment of recycled containers filled with original ink. The used ink tanks only can be returned to the dealer or the manufacturer""s service department for proper disposal. The use of exactly copied pirated ink reservoirs, unfortunately, also cannot be prevented in this device.
An object of the present invention is to provide a method for determining the number of normal imprints that can be printed with a quantity of ink remaining in an ink tank cassette which is suitable for a device with an ink jet print head that must be cleaned at intervals, whereby an amount of ink is consumed that is affected by a tolerance. The calculated quantity of remaining ink should nonetheless deviate so little from the actually available amount at the end of ink that a last normal imprint is certain to be completely printed and that a quantity remains in the ink tank cassette that is less than that required for a normal imprint. Although an employment of a refilled ink tank should be tolerated, the employment of expired, old inks for refilling an ink tank or of ink having poor quality should be made more difficult and, ultimately, largely minimized, particularly with pirated products.
The invention is based on the perception that it is of no interest whether the indication of the available ink quantity is precise at the beginning of consumption. On the contrary, the precise indication of the remaining quantity as the end of consumption approaches is of interest. After a rough identification of the remaining ink quantity, thus, an averaging over the number of normal imprints that are still possible can ensue. A pre-condition for such an averaging is the validity of an input authorization code for an ink tank cassette. The fine computational determination of the remaining number of normal imprints only ensues after a predetermined remaining ink quantity is acquired by a sensor and signaled. In the inventive method, beginning with a predetermined point in time, the number of rinses and the number of different normal imprints are taken into consideration in the computational determination, and the remaining amount is displayed as a whole number of normal imprints. The sensor acquired, predetermined remaining ink quantity is a reserve quantity intended for consumption that enables a predetermined number of normal imprints beginning with aforementioned point in time. A cleaning procedure is prevented when the ink consumption is higher than the ink consumption for a normal imprint.
The normal imprints that can be performed with an ink tank fill of the replaced ink tank cassette are identified in a rough approximation and in a user-specific manner. The most frequent user or users are acquired and the consumption is converted into the corresponding number of franking imprints either computationally or on the basis of empirically acquired data.
Experience has shown that the amount of mail franked by a user with the postage meter machine after every activation until the machine is turned off usually does not lie far from an average number of normal imprints. The latter, however, can vary greatly from user to user. For this reason and because a cleaning cycle with considerable ink consumption is triggered every time the machine is turned on, a user-specific average value thus arises for the consumption per activation cycle, i.e. during operation after turn-on until the postage meter machine is turned off. A user-specific maximum value of normal imprints that can be achieved per ink tank fill is ultimately empirically derived. Proceeding from the average, user-specific consumption, a plurality of average, normal imprints that are still possible can be derived. It is inventively provided that a normalized consumption converted into piece numbers of pseudo imprints or normal imprints is subtracted from a start number. The rough identification of the number of imprints that can be implemented ensues in a user-specific manner by the result of the aforementioned subtraction being multiplied by a yield factor u.
The postage meter machine is inventively equipped with an arrangement for recognizing a necessity for changing the consumable (ink, ink cassette), whereby the check of the validity of an input authorization code being implemented given a change. A remaining quantity of possible imprints is identified and displayed from the very beginning only when the employment of the think tank cassette is authorized. The rough calculation already begins before an output of an end of ink signal, i.e. long before the reserve quantity for consumption is tapped into.
Piracy protection for consumables based on the authentication and authorization thereof can ensue with a self-check by the device or an external check. The device has an input unit for the authorization code. The manufacturer supplies a code aggregated to the consumable. If the postage meter machine device has a chip card read/write unit available to it, the input of code and, potentially, further data can advantageously ensue from a chip card that was supplied together with the consumable ink tank cassette. The microprocessor of the device is programmed:
to make rough computational determination of the number of normal imprints that can be performed with a remaining ink quantity and for the signaling thereof before a point in time at which the predetermined remaining ink quantity acquired by the sensor is signaled as reserve;
to generate a message after a detection of the replacement of the ink tank cassette and to display it by display and wait for an input of a code with the input means;
to implement a check of the input code for authorizing the replacement ink tank cassette and to modify the operation of the device when the completed check of the code has yielded an invalidity; as well as
to make a fine computational determination of the number beginning with a point in time at which the predetermined remaining ink quantity acquired by the sensor is signaled.
An advance signaling is especially advantageous given large-scale users. Via a user interface, the user can freely program a threshold for the signaling as a reference value. This advantage is lost given the use of pirated products or refilled ink tank cassettes. The change in operation of the device can be comprised therein that the need to replace the ink tank cassette is no longer signaled before the reserve quantity for consumption is tapped into.